We have investigated the electronic structure near the band edges in intrinsic and heavily n-type doped GaN and AlN. Both the wurtzite and the zincblende polytypes have been considered. The electronic structures of the intrinsic materials were obtained from a full-potential linearized augmented plane wave calculation. We show the importance of performing a fully relativistic calculation. For instance, the hole mass in cubic AlN is a very large and negative quantity if spin-orbit coupling is excluded, whereas the fully relativistic calculation gives a relatively small and positive value. The electron-phonon coupling was taken into account according to the Fröhlich Hamiltonian for large polarons, resulting in effective polaron masses. The effects on the effective electron masses due to doping were investigated by using a Green's function formalism within the random phase approximation and with a local-field correction according to Hubbard.
The electron effective g factor tensor in asymmetric III-V semiconductor quantum wells (AQWs) and its tuning with the structure parameters and composition are investigated with envelope-function theory and the ´k p 8 8 • Kane model. The spin-dependent terms in the electron effective Hamiltonian in the presence of an external magnetic field are treated as a perturbation and the g factors * ĝ and * g , for the magnetic field in the QW plane and along the growth direction, are obtained analytically as a function of the well width L. The effects of the structure inversion asymmetry (SIA) on the electron g factor are analyzed. For the g-factor main anisotropy * * D = -^ AQWs are presented and discussed with the available experimental data; in particular InAs QWs are shown to not only present much larger g factors but also a larger g-factor anisotropy, and with the opposite sign with respect to GaAs QWs.
The band gap shift (BGS) of Si-doped wurtzite GaN for impurity
concentrations spanning the insulating to the metallic regimes has been
investigated at low temperature. The critical impurity concentration for
the metal-non-metal transition is estimated from the generalized Drude
approach for the resistivity to be about 1.0×1018 cm-3.
The calculations for the BGS were carried out within a framework of the
random phase approximation, taking into account the electron-electron,
electron-optical phonon, and electron-ion interactions. In the wake of
very recent photoluminescence measurements, we have shown and discussed the
possible transitions involved in the experimental results.
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